(S)-5-chloro-N-((3-(4-(5,6-dihydro-4H-1,2,4-oxadiazin-3-yl)phenyl)-2-oxooxazolidin-5-yl)methyl)thiophene-2-carboxamide of Formula (I-A) serves as an inhibitor against blood coagulation factor Xa and can be used for treating and preventing thrombosis, myocardial infarction, arteriosclerosis, inflammatory, apoplexy, angina pectoris, recurrent stricture after angioplasty, and thromboembolism such as intermittent claudication.

The method for preparing the above-mentioned compound having an inhibitory effect against factor Xa is disclosed in Korean Patent No. 898361 which is filed by the present inventors. However, said method has problems in that the total production yield is low and column chromatography must be employed in the purification process of each step, which makes it not suitable for mass production.